1. Field of the Invention
The invention relates to an apparatus for filling a hole formed with a liquid crystal display cell and a method of doing the same, and more particularly to such an apparatus and a method both capable of making it possible to allowing a curable resin to reach at a predetermined position in the hole.
2. Description of the Related Art
FIG. 1 is an exploded perspective view of a liquid crystal display cell. A liquid crystal display cell 100 used for a thin film transistor (TFT) active matrix type color liquid crystal panel is generally comprised of a thin film transistor substrate (hereinafter, referred to as "TFT substrate") 101 and a color filter substrate (hereinafter, referred to as "CF substrate") 102. These TFT substrate 101 and the CF substrate 102 are adhered to each other with a small gap therebetween so that the adhered substrates 101 and 102 make a hollow space therein and the hollow space is communicated to atmosphere through an injection hole 104. Liquid crystal is injected into the hollow space through the injection hole 104. Thus, the liquid crystal display cell 100 is completed.
TFT substrate 101 is designed to have an alignment film on a surface on which TFT has been fabricated. An adhesive 103 which is to be cured when heated is applied to a region outside a display region 105 of the surface of TFT substrate 101. Then, TFT substrate 101 and CF substrate 102 are overlapped with spacers 106 being sandwiched therebetween. TFT substrate 101 and CF substrate 102 are adhered to each other by heating and pressurizing them to thereby bake the adhesive 103.
In order to inject liquid crystal into a space formed between TFT substrate 101 and CF substrate 102, when the adhesive 103 is applied to a region outside the display region 105, there is formed an injection hole 104 through which liquid crystal is to be injected into the above-mentioned space.
Liquid crystal is injected into the space as follows. First, the liquid crystal display cell 100 is put into vacuum atmosphere. Then, as illustrated in FIG. 2, the liquid crystal display cell 100 is downwardly moved in a direction indicated with an arrow so that the injection hole 104 makes contact with liquid crystal 108 contained in a liquid crystal plate 107. Then, the vacuum atmosphere around the liquid crystal display cell 100 is turned into atmospheric pressure. As a result, the liquid crystal 108 is absorbed into the space due to a difference in pressure between inside and outside the liquid crystal display cell 100.
After the liquid crystal 108 has been introduced into the space, the injection hole 104 is closed by means of a resin which is cured when ultraviolet ray is radiated thereto. After the injection hole 104 has been filled with the resin and the resin has been applied around the hole 104, the resin is cured by radiating ultraviolet ray thereto from a ultraviolet lamp standing in a predetermined position.
However, as illustrated in FIGS. 3A and 3B, a gap .beta. of the injection hole 104 through which the liquid crystal 108 is introduced into the space may be expanded greater than a gap defined by the spacers 106, or may be not uniform in liquid crystal display cells. Thus, there may be caused a problem that the resin 109 to be cured when ultraviolet ray is radiated thereto unpreferably enters the display region 105 of the liquid crystal display cell 100, resulting in defectiveness in display in the liquid crystal display cell 100.
In addition, there may be caused another problem that a distance .alpha. by which the resin 109 enters the injection hole 104 is not uniform in liquid crystal display cells, resulting in deterioration in a fabrication yield.
For instance, Japanese Unexamined Patent Publication No. 8-160440 (hereinafter, referred to as "first prior art") has suggested a liquid crystal display cell capable of overcoming the above-mentioned problems. FIG. 4A is a perspective view illustrating a liquid tight container suggested in the first prior art, and FIG. 4B is a cross-sectional view illustrating a resin is being introduced into the liquid tight container.
As illustrated in FIG. 4A, a container 200 is comprised of first and second glass substrates 201 and 202 adhered to each other with a sealing frame 203 being sandwiched therebetween. The sealing frame 203 is formed with a tunnel-like gap 204 through which liquid crystal is introduced into the container 200.
In order to seal the gap 204, the gap 204 is first dipped into a resin pool 231. As a result, as illustrated in FIG. 4B, the resin 231 is upwardly absorbed in the gap 204 in a direction indicated with arrows, and further enters the sealing frame 203 from a position C to a position H.
While the resin 231 is being absorbed in the gap 241, a light is radiated to at least a top H of the resin 231 to thereby cure the resin 231 in the gap 204.
In accordance with the first prior art, it would be possible to cure a top of the resin 231 in the desired form by pattering a light to be radiated to the resin 231 to cure the resin 231, and to prevent the resin 231 to further enter the container 200 beyond the top H thereof.
Japanese Unexamined Patent Publication No. 6-160873 (hereinafter, referred to as "second prior art") has suggested a method and an apparatus for closing a hole through which liquid crystal has been introduced into a liquid crystal display panel, with a resin which is to be cured when ultraviolet ray is radiated thereto. FIG. 5 is a side view of an apparatus for closing the hole, suggested in the second prior art.
As illustrated in FIG. 5, a plurality of liquid crystal display panels are fixed by a jig 302 on a carrier plate 303 so that a hole through which liquid crystal is introduced into a liquid crystal display panel is upwardly directed. An applicator base 305 on which an automatic applicator 304 and a driver therefor are mounted receives a rotational force 306 generated by a motor 306, transmitted through a ball screw 307, and moves in a direction indicated with an arrow A.
When a jig sensor detects the jig 302, the applicator base 305 is caused to stop. Then, the automatic applicator 304 moves to a predetermined position, and successively applies a resin to the liquid crystal display panels. Herein, the applied resin is a resin which is cured when ultraviolet ray is radiated thereto.
After the application of the resin to the liquid crystal display panels has been finished, the carrier plate 303 on which the jig 302 is mounted is guided by a linear guide bearing 320 and moved in a direction indicated with an arrow B by a rotational force of a motor 318, transferred through a ball screw 319.
When a jig sensor 321 detects the jig 302, the carrier plate 303 is caused to stop. After the carrier plate 303 has been caused to stop, a cylinder 324 moves in the left to thereby open a shutter 323 of an ultraviolet ray lamp 322 for a certain period of time. Thus, the ultraviolet ray lamp 322 radiates ultraviolet ray to the resin having been applied to the liquid crystal display panels.
After ultraviolet ray has been radiated to the resin having been applied to all the liquid crystal display panels mounted on the jig 302, the carrier plate 303 returns to its original position. Thus, a cycle of an operation for closing the hole finishes.
In the above-mentioned first prior art, a resin for sealing the hole 204 can be cured at a desired position in the hole 204 by always radiating a light to the desired position.
However, the first prior art is accompanied with a problem that since a light is radiated through the glass substrate 201 or 202, a light is decayed, resulting in that the resin 231 enters the container 200 beyond a desired position to which a light is always radiated, without being cured.
The first prior art is accompanied with another problem that since a light is radiated through the glass substrate 201 or 202, a light is decayed, resulting in that a curing rate of the resin 231 is reduced. As a result, an accelerating agent contained in the resin 231 for accelerating the resin 231 to cure leaks into liquid crystal, which would bring defectiveness in display in the liquid crystal display.
In accordance with the above-mentioned second prior art, a resin to be cured when ultraviolet ray is radiated thereto is automatically applied to a hole through which liquid crystal has been introduced into the liquid crystal display panel. Hence, it is possible to keep amount and length of an applied resin constant. In addition, since the resin is cured under control for a total amount of ultraviolet ray, it would be possible to stably, successively cure the resin.
However, the second prior art does not have a controller for controlling a distance by which the resin reaches in the hole of the liquid crystal display panel. As a result, the second prior art is accompanied with such a problem as having been explained with reference to FIGS. 3A and 3B.